The present invention relates to a new and improved construction of a clutch arrangement for a marine vessel drive or propulsion system.
Generally speaking, the clutch arrangement for the marine vessel drive or propulsion system of the present development is of the type comprising a normally driving or drive first shaft which is connected by means of a first drive-side toothed clutch half of a synchronizing jaw or tooth clutch as well as with a primary part of a fluid coupling or a fluid or torque converter. There is also provided a normally driven second shaft which is connected with a power take-off side toothed clutch half of the tooth clutch as well as with a secondary part of the fluid coupling or the fluid or torque converter. The tooth or jaw clutch possesses a clutch star which, by means of a first tooth system at one of the toothed clutch halfs, is axially displaceably guided by continuous meshing of the teeth and can be engaged by a second tooth system with the second clutch half and carries a pawl blocking device. This pawl blocking device engages upon passing through a synchronous rotational speed and causes a screw-like relative movement of two parts or components of the tooth clutch which causes the engagement of the clutch star.
A state-of-the-art clutch arrangement of this type has been disclosed in the article of E. Fortunato and H. A. Clements, entitled "Marine Reversing Gear Incorporating Single Reversing Hydraulic Coupling and Direct-Drive Clutch for Each Turbine", appearing in the 1979 publication of ASME. With such prior art clutch arrangement the continuously meshing teeth of the clutch star and the one clutch half are constructed as helical teeth, so that the clutch star can be directly threaded onto this one clutch half, and thus, can be engaged with its second tooth system in the second clutch half. The pawl blocking device consists of a ring-shaped pawl support attached at the clutch star and containing pawls mounted thereat and a pawl tooth system formed at the second clutch half into which there can engage the pawls. With completely disengaged tooth or jaw clutch the pawl support assumes an axially offset position in relation to the pawl teeth, at which the pawl blocking device is completely ineffective and during forward rotation of the first shaft renders possible both forward rotation as well as reverse rotation of the second shaft. Secured to the second shaft is a bearing ring upon which there is mounted a brake ring in such a manner that the friction prevailing between both rings strives to retain the brake ring at the rotational speed of the second shaft. The brake ring possesses helical teeth into which there axially displaceably engage helical teeth formed at the pawl support. These helical teeth convert the braking moment transmitted from the bearing ring to the brake ring into an axial force which is effective at the pawl support. This axial force strives to retain the pawl blocking device in its ineffectual position as long as the second shaft rotates forwardly at a smaller velocity than the first shaft or the second shaft is stationary or rotates backwards.
In order to initiate an engagement operation of the known jaw or tooth clutch, the clutch star can be shifted, and along therewith the pawl support by means of a servomotor, in such a manner that the pawls come into engagement with the pawl teeth. However, such displacement must be positively prevented during the normal operating state of the fluid or hydraulic coupling, when the drive shaft rotates at a greater angular velocity than the power take-off shaft, since otherwise the pawl blocking device can be damaged. It is for this reason that there is operatively correlated with the clutch arrangement a measuring and control device which continuously monitors and compares the angular velocities of both shafts and only then allows for actuation of the servomotor when the rotational speed of the first shaft drops below that of the second shaft. If the tooth or jaw clutch should be engaged it is thus always necessary to brake the first shaft, and along therewith the related drive machine, to an angular velocity below that retained by the second shaft during ahead travel of the vessel because of the propellor thrust. Only then is it possible for the servomotor to displace the clutch star together with the pawl support into an intermediate position where the pawls can coact with the pawl teeth and initially ratchet thereover. Thereafter, if the drive machine is gradually again speeded-up, then the pawls engage with the pawl teeth and prevent the pawl support together with the clutch star, from assuming in conjunction with the drive shaft an angular velocity which is greater than that of the power take-off shaft. The clutch star thus remains in its angular velocity behind that of the drive shaft, so that the clutch star can be displaced in the engaging sense by the intermeshing helical teeth which connect such with the first clutch half, until the second teeth or tooth system of the clutch star has engaged with the second clutch half and the clutch star has reached an impact or contact position.
The necessity of braking the first shaft, and thus the entire drive machine, in the described manner before the synchronization operation can begin with gradually again increasing angular velocity of the drive shaft, constitutes an appreciable loss in time which can arise already at an initial or pre-phase of the engagement of the tooth or jaw clutch. This loss in time can significantly reduce the mobility of a marine vessel equipped with the prior art clutch arrangement. In the event that the servomotor brings the pawl blocking device into engagement prior to the angular velocity of the first shaft having been sufficiently lowered, for instance because of failure of the described control device, then the pawl blocking device will be damaged. Consequently, the tooth or jaw clutch will be unusable and the marine vessel drive or propulsion system must be shutdown in order to avoid even greater damage.